Secondary treatment is treating wastewater in a municipal water system that removes most contaminants from wastewater by reducing their levels to acceptably low levels. In other words, it helps to reduce the pollutants in water-contaminating substances such as organic matter, heavy metals, and chemical compounds.
Full Answer
What are the different types of Secondary contaminants that can be removed?
Conventional treatments will remove a variety of secondary contaminants. Coagulation (or flocculation) and filtration removes metals like iron, manganese and zinc. Aeration removes odors, iron, and manganese. Granular activated carbon will remove most of the contaminants which cause odors, color, and foaming.
Does EPA enforce secondary maximum contaminant levels (smcls)?
EPA does not enforce these "secondary maximum contaminant levels" ( SMCLs). They are established as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color, and odor.
What is the EPA definition of secondary treatment?
The United States Environmental Protection Agency (EPA) defined secondary treatment based on the performance observed at late 20th-century bioreactors treating typical United States municipal sewage. Secondary treated sewage is expected to produce effluent with a monthly average of less than 30 mg/l BOD and less than 30 mg/l suspended solids.
What is secondary settling in wastewater treatment?
Secondary treatment consists of a biological process and secondary settling is designed to substantially degrade the biological content of the sewage such as are derived from human waste, food waste, soaps and detergent. The majority of municipal and industrial wastewater plants treat the settled sewage liquor using aerobic biological processes.
What does secondary treatment not remove?
Michigan Environmental Education Curriculum. Wastewater Treatment. Microorganisms such as bacteria and protozoa can use the small particles and dissolved organic matter, not removed in primary treatment, as food.
What is removed during secondary treatment?
Secondary treatment removes the soluble organic matter that escapes primary treatment. It also removes more of the suspended solids. Removal is usually accomplished by biological processes in which microbes consume the organic impurities as food, converting them into carbon dioxide, water, and energy…
What does secondary treatment of wastewater remove?
Secondary treatment is the removal of biodegradable organic matter (in solution or suspension) from sewage or similar kinds of wastewater. The aim is to achieve a certain degree of effluent quality in a sewage treatment plant suitable for the intended disposal or reuse option.
What happens to the remaining dirt in secondary treatment?
What happens to the remaining dirt? The dirt sinks and is pumped out of the system.
What contaminant is removed by tertiary treatment?
Tertiary water treatment is the final stage of the multi-stage wastewater cleaning process. This third stage of treatment removes inorganic compounds, bacteria, viruses, and parasites. Removing these harmful substances makes the treated water safe to reuse, recycle, or release into the environment.
What happens in secondary treatment plant?
Secondary wastewater treatment processes use microorganisms to biologically remove contaminants from wastewater. Secondary biological processes can be aerobic or anaerobic, each process utilizing a different type of bacterial community.
What is the main goal of secondary wastewater treatment?
The objective of secondary treatment is the further treatment of the effluent from primary treatment to remove the residual organics and suspended solids.
What happens to sewage after treatment?
What happens to the treated water when it leaves the wastewater treatment plant? The treated wastewater is released into local waterways where it's used again for any number of purposes, such as supplying drinking water, irrigating crops, and sustaining aquatic life.
What are the major objectives of the secondary wastewater treatment?
The main objective of secondary treatment: To remove most of the fine suspended and dissolved degradable organic matter that remains after primary treatment, so that the effluent may be rendered suitable for discharge.
What happens to sludge from a sewage treatment plant?
Once treated, sewage sludge is then dried and added to a landfill, applied to agricultural cropland as fertilizer, or bagged with other materials and marketed as “biosolid compost” for use in agriculture and landscaping.
What happens to sludge in septic tank?
Bacteria that lives in the tank helps to break down the sludge, turning it into a liquid. Near the top of the septic tank is a pipe that leads to a part of the yard called the drain field. When the waste water in the septic tank reaches this pipe, the water flows into the drain field and is filtered through the soil.
What happens during the last step of the waste treatment?
The last step of primary treatment involves sedimentation, which causes the physical settling of matter. Sedimentation often uses chemicals like flocculants and coagulants.
Secondary Contaminants
Often added to municipal water in the course of treatment, as well as naturally occurring. High levels of aluminum may cause discoloration of water.
Other Aesthetic Drinking Water Factors
HARDNESS is a measure of dissolved minerals in water, mainly calcium and magnesium. The hardness scale is as follows: 0-75 soft, 75-150 moderately hard, 150-300 hard, over 300 is very hard.
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Secondary Treatment Definition
Secondary treatment of wastewater is a process that follows the primary treatment of sewage.
Objectives of Secondary Treatment
The objectives of secondary treatment are to remove the remaining suspended solids, BOD, and COD from the wastewater. It is done to reduce the primary clarifier load and improve the quality of the effluent discharged from the treatment plant.
What are the Stages of Wastewater Treatment?
The stages of wastewater treatment are collection, pre-treatment, primary treatment, secondary treatment, tertiary treatment, disposal, and reuse.
What is The Secondary Treatment of Wastewater?
This article will tell you about the second stage in the wastewater treatment process.
How Does Secondary Treatment Work
Secondary treatment is treating wastewater in a municipal water system that removes most contaminants from wastewater by reducing their levels to acceptably low levels.
What are The Alternative Types of Secondary Biological Processes?
There are a few different types of alternative secondary biological processes, and these include aerobic and anaerobic processes.
Conclusion
The secondary wastewater treatment process is more complicated than the primary wastewater treatment process. It is necessary to remove the remaining pollutants from the wastewater. The method includes various other activities that can remove the remaining impurities.
What are the problems with secondary contaminants?
These problems can be grouped into three categories: Cosmetic effects — effects which do not damage the body but are still undesirable. Technical effects — damage to water equipment or reduced effectiveness of treatment for other contaminants.
Why do disinfectants have color?
Color may be indicative of dissolved organic material, inadequate treatment, high disinfectant demand, and the potential for the production of excess amounts of disinfectant by-products. Inorganic contaminants such as metals are also common causes of color.
What are the problems with water?
These problems can be grouped into three categories: 1 Aesthetic effects — undesirable tastes or odors; 2 Cosmetic effects — effects which do not damage the body but are still undesirable 3 Technical effects — damage to water equipment or reduced effectiveness of treatment for other contaminants
What is the EPA drinking water regulation?
EPA has established National Primary Drinking Water Regulations National Primary Drinking Water Regulations Legally enforceable standards that apply to public water systems. These standards protect drinking water quality by limiting the levels of specific contaminants that can adversely affect public health and which are known or anticipated ...
What is the best treatment for odors?
Coagulation (or flocculation) and filtration removes metals like iron, manganese and zinc. Aeration removes odors, iron, and manganese. Granular activated carbon will remove most of the contaminants which cause odors, color, and foaming.
What are the effects of corrosive water?
Other effects of corrosive water, such as the corrosion of iron and copper, may stain household fixtures and impart objectionable metallic taste and red or blue-green color to the water supply. Corrosion of distribution system pipes can reduce water flow.
Does corrosion control remove metals from water?
By controlling these factors, the public water system can reduce the leaching of metals such as copper, iron, and zinc from pipes or fixtures, as well as the color and taste associated with these contaminants. It should be noted that corrosion control is not used to remove metals from contaminated source waters.
What is secondary wastewater treatment?
Secondary Wastewater treatment is the second stage of wastewater treatment. In primary treatment, suspended solids, colloidal particles, oil, and grease are removed. In secondary treatment, biological treatment is done on the wastewater to remove the organic matter present. This treatment is performed by indigenous and aquatic micro-organisms like ...
What is the process that uses oxygen to break down organic matter and remove other pollutants?
These processes are sensitive to temperature and with an increase in temperature, the rate of biological reactions increases. 1. Aerobic Treatment: Aerobic wastewater treatment is a biological treatment that uses oxygen to break down organic matter and remove other pollutants like nitrogen and phosphorus.
What is an anoxic condition?
The anoxic conditions simply ensure that nitrate will serve as an “electron acceptor” in the dissimilation process instead of oxygen. In pre-anoxic basin influent wastewater, return sludge from the clarifier, and nitrate-rich mixed liquor pumped from the effluent end of the aeration tanks are mixed together.
What is SBR treatment?
It is used to reduce the organic matter (BOD and COD), oxygen is bubbled with a mixture of wastewater and activated sludge. After this treatment, the treated water can be discharged on surface water.
What is a membrane bioreactor?
Membrane Bioreactor – MBR is the combination of ultrafiltration (UF) and activated sludge process. MBR produces effluent of high quality which can be discharged to surface water for reuse. It can be retrofitted in existing installations.
Why is the sludge digestion system rendered simple?
However, the operation is rendered simple due to the elimination of primary settling and separate sludge digestion.
Can anaerobic bacteria use oxygen?
However, anaerobic bacteria can and will use oxygen that is found in the oxides introduced into the system or they can obtain it from organic material within the wastewater. Anaerobic treatment technology is Up-flow Anaerobic Sludge Blanket Reactor (UASB)
What happens when biocide concentrations exceed the secondary treatment?
BOD reduction normally accomplished by that species temporarily ceases until other species reach a suitable population to utilize that food source, or the original population recovers as biocide concentrations decline.
What is secondary treatment?
Secondary treatment is designed to substantially degrade the biological content of the sewage which are derived from human waste, food waste, soaps and detergent. The majority of municipal plants use aerobic biological processes as a secondary treatment step. To be effective, the biota require both oxygen and food to live.
How much BOD is in secondary treated sewage?
Secondary treated sewage is expected to produce effluent with a monthly average of less than 30 mg/l BOD and less than 30 mg/l suspended solids. Weekly averages may be up to 50 percent higher.
How is primary clarifier effluent discharged?
Primary clarifier effluent was discharged directly to eutrophic natural wetlands for decades before environmental regulations discouraged the practice. Where adequate land is available, stabilization ponds with constructed wetland ecosystems can be built to perform secondary treatment separated from the natural wetlands receiving secondary treated sewage. Constructed wetlands resemble fixed-film systems more than suspended growth systems, because natural mixing is minimal. Constructed wetland design uses plug flow assumptions to compute the residence time required for treatment. Patterns of vegetation growth and solids deposition in wetland ecosystems, however, can create preferential flow pathways which may reduce average residence time. Measurement of wetland treatment efficiency is complicated because most traditional water quality measurements cannot differentiate between sewage pollutants and biological productivity of the wetland. Demonstration of treatment efficiency may require more expensive analyses.
What is a cyclic activated sludge system?
One type of system that combines secondary treatment and settlement is the cyclic activated sludge (CASSBR), or sequencing batch reactor (SBR). Typically, activated sludge is mixed with raw incoming sewage, and then mixed and aerated. The settled sludge is run off and re-aerated before a proportion is returned to the headworks.
What is primary treatment of sewage?
Primary treatment of sewage by quiescent settling allows separation of floating material and heavy solids from liquid waste. The remaining liquid usually contains less than half of the original solids content and approximately two-thirds of the BOD in the form of colloids and dissolved organic compounds.
What is the biological stage of a high charged system?
This refers to the way the biological load is processed. In high charged systems, the biological stage is presented with a high organic load and the combined floc and organic material is then oxygenated for a few hours before being charged again with a new load.
What is the most effective method of secondary treatment of wastewater?
This method of secondary treatment of wastewater employs sand filters, contact filters, or trickling filters to ensure that additional sediment is removed from wastewater. Of the three filters, trickling filters are typically the most effective for small-batch wastewater treatment.
What is primary treatment of wastewater?
Primary treatment of wastewater involves sedimentation of solid waste within the water. This is done after filtering out larger contaminants within the water. Wastewater is passed through several tanks and filters that separate water from contaminants.
How long does it take for a wastewater solution to be aerated?
The resulting mixture is then aerated for up to 30 hours at a time to ensure results.
What is the third step in wastewater management?
This third and last step in the basic wastewater management system is mostly comprised of removing phosphates and nitrates from the water supply. Substances like activates carbon and sand are among the most commonly used materials that assist in this process.
What are the three main stages of sewage treatment?
The three standard sewage-treatment stages include primary, secondary, and tertiary steps . Primary treatment is almost always applied.
What happens if no further treatment is performed?
If no further treatment is performed, the wastewater is disinfected by the addition of chlorine and discharged into a stream or a body of water. If further treatment is needed, the wastewater goes through the secondary-treatment step. Secondary treatment.
What is biological oxidation?
The process—called biological oxidation—involves trickling filters, activated sludge, and stabilization ponds. Unless tertiary treatment will be used, the wastewater is disinfected with chlorine and then discharged. Sludge remaining from the primary- and secondary-treatment processes is sent to a sludge digester for further processing.
How long does it take for sludge to digest?
The digester relies on aerobic bacteria to break down volatile matter in the sludge over the course of two or three weeks.
What is sewage treatment?
Sewage-treatment plants use a series of steps to remove any biological and chemical contaminants that are a risk to human health or the environment. Such plants eliminate final traces of suspended solids; halt the undesirable growth of algae; reduce nutrient content; and remove undesirable taste, color, and odor.
Is tertiary treatment always used?
Although secondary treatment is recommended for most sewage, many plants are not equipped to perform it. Tertiary treatment, a relatively expensive cleansing step, is used even less frequently, usually only when water of drinking quality is desired. Primary treatment.